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Artículo
Fragments of Arithmetic and true sentences
(Wiley, 2005)
By a theorem of R. Kaye, J. Paris and C. Dimitracopoulos, the class of the ¦n+1–sentences true in the standard model is the only (up to deductive equivalence) consistent ¦n+1–theory which extends the scheme of induction ...
Artículo
Some Results on LΔ n+1
(Wiley, 2001)
We study the quantifier complexity and the relative strength of some fragments of arithmetic axiomatized by induction and minimization schemes for Δn+1 formulas.
Artículo
Existentially Closed Models and Conservation Results in Bounded Arithmetic
(Oxford Academic, 2009)
We develop model-theoretic techniques to obtain conservation results for first order Bounded Arithmetic theories, based on a hierarchical version of the well-known notion of an existentially closed model. We focus on the ...
Artículo
Induction, minimization and collection for Δ n+1 (T)–formulas
(Springer, 2004)
For a theory T, we study relationships among IΔ n +1 (T), LΔ n+1 (T) and B * Δ n+1 (T). These theories are obtained restricting the schemes of induction, minimization and (a version of) collection to Δ n+1 (T) formulas. ...
Artículo
On the quantifier complexity of Δ n+1 (T)– induction
(Springer, 2004)
In this paper we continue the study of the theories IΔ n+1 (T), initiated in [7]. We focus on the quantifier complexity of these fragments and theirs (non)finite axiomatization. A characterization is obtained for the class ...
Artículo
A Note on Σ₁-Maximal Models
(Association for Symbolic Logic, 2007)
Let T be a recursive theory in the language of first order Arithmetic. We prove that if T extends: (a) the scheme of parameter free Δ₁-minimization (plus exp), or (b) the scheme of parameter free Π₁-induction, then there ...
Artículo
Envelopes, indicators and conservativeness
(Wiley, 2006)
A well known theorem proved (independently) by J. Paris and H. Friedman states that BΣn +1 (the fragment of Arithmetic given by the collection scheme restricted to Σn +1‐formulas) is a Πn +2‐conservative extension of IΣn ...